....adding to a "character skill book" is still making it an in-organic book keeping process rather than something that is inherently part of the character.
I think making the game "classless" is way of dumbing the game down and the skill books is just a lazy way of accommodating that. What the player ends up with is big mess of vendors you have to visit to find the books to upgrade certain class skills. It doesn't add anything to the game it just makes it more tedious.
Better that if I ding a level I can just select my character sheet and make choices straight away rather than having to remember which vendor to visit to get the skill book I need.